Almost all of magenta color image forming couplers which have been widely used in the art are 5-pyrazolones. It is known that the dyes formed upon the coupling of 5-pyrazolone type couplers with the oxidation products of aromatic primary amine developing agents have an undesirable subsidiary absorption of the yellow component in the region around 430 nm which causes color turbidity.
In order to reduce the yellow component, a pyrazolobenzimidazole nucleus, as described in British Pat. No. 1,047,612; an indazolone nucleus, as described in U.S. Pat. No. 3,770,447; and a pyrazolo[5,1-c]-1,2,4-triazole nucleus, as described in U.S. Pat. No. 3,725,067, have been proposed as a magenta color image forming coupler skeleton. However, the magenta couplers described in these patents are still insufficient because they provide only poor color images when they are mixed with a silver halide emulsion in the form of a dispersion in a hydrophilic protective colloid such as gelatin, they have a low solubility in an organic solvent having a high boiling point, they are difficult to synthesize, or the light-fastness of dyes formed therefrom is very poor.
The above-described problems have been solved by the development of magenta couplers having a 1H-pyrazolo[1,5-b]-1,2,4-triazole nucleus as described in Japanese Patent Application (OPI) No. 171956/84 (the term "OPI" as used herein means "unexamined published patent application") and U.S. Pat. No. 4,540,654. The above-described 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers have many features in that they provide color images which do not have an undesirable absorption of the yellow component as formed from 5-pyrazolone type couplers, they have a sufficiently high solubility in an organic solvent having a high boiling point, they are easily synthesized, and they provide color images having good light-fastness.
However, it has been found that 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers having a halogen atom, an alkylthio group or an arylthio group, etc. as a coupling split-off group, which can be easily synthesized, are generally insufficient with respect to sensitivity and gradation (.gamma.) .
In order to achieve the most preferred color reproduction, it is required that the maximum absorption wavelength of the color images formed from magenta couplers have the most appropriate certain value. This value is generally present in a range from 530 nm to 570 nm, although it can be varied depending on the kind of color photographic light-sensitive materials in which the magenta couplers are employed, for example, whether the magenta couplers are used in color negative films, color reversal films, or color papers, etc., or on the values of the maximum absorption wavelength of the color images formed from cyan couplers and yellow couplers which are employed in combination with the magenta couplers. Thus, when the optimum value is selected in the range, the above-described 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers can provide the most preferred color reproducibility coupled with no subsidiary yellow absorption in the region around 430 nm as described above.
However, the maximum absorption wavelength of color images formed from known 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers is present in a very narrow range of from about 540 nm to bout 550 nm. Therefore, these known 1H-pyazolo[1,5-b]-1,2,4-triazole magenta couplers have a problem that while these couplers show a desirable color reproducibility in cases where they are employed in certain color photographic light-sensitive materials and in combination with specified cyan couplers and yellow couplers, they cannot always provide a desirable color reproducibility when they are employed in other color photographic light-sensitive materials or when they are employed in combination with other cyan couplers or yellow couplers.
The maximum absorption wavelength of color images formed from the above-described 1H-pyrazolo[5,1-c]-1,2,4-triazole magenta couplers can be controlled by the selection of an organic solvent for dispersion having a high boiling point which is utilized in order to incorporate these couplers into silver halide color photographic materials in the form of an emulsified dispersion. However, according to such a method, the degree of control is small and other problems are apt to be accompanied in that the sensitivity and gradation (.gamma.) are decreased, stain occurs, and the light-fastness of color images formed degradates. Accordingly, known 1H-pyrazolo[1,5-b]-1,2,4-triazole magenta couplers or 1H-pyrazolo[5,1-c]-1,2,4-triazole magenta couplers are not satisfactory for obtaining color images having high sensitivity and gradation, good light-fastness, and preferred color reproducibility without the occurrence of stain.